Fluorescent lamp circuit



y 30, 1967 R. A. VANASSE 3,323,007

FLUORESCENT LAMP CIRCUI T Filed Nov. 13, 1963 INVENTOR. @ym/mf .17. Vaws'e f ww w United States Patent 3,323,007 FLUORESCENT LAMP CIRCUIT Raymond A. Vanasse, Marblehead, Mass., assignor to Sylvania Electric Products Inc., a corporation of Delaware Filed Nov. 13, 1963, Ser. No. 323,481 4 Claims. (Cl. 315-99) This invention relates to fluorescent lamp circuits, particularly a starting circuit for a low pressure fluorescent lamp of the preheat type.

Preheat fluorescent lamps have two spaced filamentary electrodes. Each electrode terminates in a pair of terminals such that the electrodes can be heated to electron emissive state by their resistance to applied alternating current. An automatic or manual switch can then disconnect heating current and apply a voltage pulse from an inductive ballast across the lamp, thereby igniting a discharge arc between the electrodes. The are is thenmaintained by alternating current.

Preheat lamps are advantageous in low wattage applications and are economical because their ballast consumes little power. However, they frequently fail to start when the ballast is connected across the tube owing to insuflicient preheating of the filamentary electrodes, or because the current through the ballast is at or near zero when the ballast is connected across the lamp. If an automatic starter is used it not only adds expense but also requires 4 to 10 seconds to start the lamp. If the arc fails to strike immediately, the automatic starting cycle may be repeated several times resulting in an objectionable flicker. If a manual starting switch is used it may have to be operated several times.

The disadvantages of a preheat lamp are accentuated when it is used in a low temperature environment, for example in a household refrigerator where it is intended that the lamp be started by a refrigerator door switch.

One object of the present invention is to provide a starting circuit for preheat lamps which insures instantaneous starting with high reliability, but at low cost. Another object is to provide a starting circuit for lamps operating in low ambient temperature conditions.

According to the invention a fluorescent lamp starting circuit comprises power terminals for supplying current to the lamp, first and second pairs of lamp terminals, first and second inductances, a first circuit connecting the first inductance and each pair of lamp terminals in series, a second circuit connecting the second inductance to two lamp terminals including one lamp terminal of each pair, and switch means in each of said circuits conjointly operative to open said circuits so that at least one inductance applies a voltage pulse across the lamp.

For the purpose of illustration a typical embodiment of the invention is shown in the accompanying drawing in which:

The single figure is a schematic diagram of a fluorescent lamp starting circuit.

As shown in the figure the starting circuit is connected between power terminals A and C, adapted to be connected to an alternating current line, and two pairs of lamp terminals 11, 12 and 13, 14 which are adapted to be connected to the filamentary electrodes E of a preheat fluorescent lamp L. One power terminal C is connected by a wire 5 directly to one lamp terminal 14; the other power terminal A is connected through a ballast L1 and wire 6 to a lamp terminal 12 of the other pair.

Lamp terminals 11 and 13 are connected through wires 7 and 8 to contacts 1 and 2 engaged by a contactor S1. These connections complete a starting circuit between the power terminals A and C which includes the inductive ballast L1 and the two pairs of lamp terminals 11, 12 and 13, 14.

-L2 is connected in a second circuit in which are a switch including a contactor S2, contacts 3 and 4 and wires 9 and 10 which through wires 5 and 6 complete the second circuit across the lamp.

The contactors S1 and S2 in the first and second circuits described are mechanically connected by a plunger S or like actuator which opens them conjointly, that is, at about the same time. For example, the contactors are held closed when a refrigerator door is closed, and opened when the door is opened.

With the starting circuit shown current in each ballast L1 and L2 follows the alternating current at power terminals A, C with a phase change dependent on the inductive reactance of the ballast. The values of ballasts L1 and L2 are chosen such that there is a phase displacement between their respective currents. For example, in a starting circuit for a 14 to 20 watt preheat lamp, values of 290 ohms for L1 and ohms for L2 produce a phase displacement of 60. When contactors S1 and S2 are open, the ballasts inductively discharge voltage pulses through the lamp with the same phase displacement. Even if the instantaneous current in one ballast is zero, the phase displacement insures that current will not be at or near zero in the other ballast and that a voltage pulse will be applied to the lamp.

The present starting circuit makes possible continuous heating of the electrodes, increased current through the conventional ballast L1 because the shunting action of ballast L2 results in higher starting pulses, and increased reliability of starting due to the phase displacement of currents in the ballasts.

It should be understood that the present invention includes all modifications and equivalents which fall within the scope of the appended claims. For example, the circuit is not restricted to use with lamps of the sizes given, but may be used with larger lamps by adjusting the values of the ballasts.

I claim:

1. A fluorescent lamp starting circuit comprising power terminals for supplying alternating current to the lamp, first and second pairs of lamp terminals, first and second magnetically independent inductances, a first circuit connecting the first inductance only and each pair of lamp terminals in series between said power terminals, a second circuit connecting the second inductance in parallel with two lamp terminals including one lamp terminal of each pair, and switch means in each of said circuits mechanically coupled and conjointly operative to open said circuits so that at least one inductance applies a voltage pulse across the lamp to ignite the lamp.

2. A preheat fluorescent lamp starting circuit comprising power terminals for supplying current to the lamp, first and second pairs of lamp terminals, first and second magnetically independent inductances, a first circuit connecting the first inductance only and each pair of lamp terminals in series between said power terminals, a second circuit including means connecting the second inductance in parallel with two lamp terminals including one lamp terminal of each pair, and switch means in each of said circuits mechanically coupled and conjointly operative to open said circuits so that at least one inductance applies a voltage pulse across the lamp to ignite the lamp, the

3 switch means in the second circuit being connected to the other lamp terminal of each pair.

3. A preheat fluorescent lamp starting circuit comprising power terminals for supplying alternating current to the lamp, first and second pairs of lamp terminals, first and second magnetically independent inductances, a first circuit connecting the first inductance only and each pair of lamp terminals in series between said power terminals, a second circuit connecting the second inductance in parallel with two lamp terminals including one lamp terminal of each pair, said inductances having different ohmic values, and switch means in each of said circuits mechanically coupled and conjointly operative to open said circuits so that at least one inductance applies a voltage pulse across the lamp to ignite the lamp.

4. A starting circuit for a low pressure, preheat fluorescent electric discharge lamp (L) having filamentary electrodes, said circuit comprising:

power terminals (A, C) adapted to be connected to an alternating current supply,

first and second pairs of lamp terminals (11, 12 and 13,

14) adapted to be connected to the filamentary electrodes (E) of said lamp,

a first inductive ballast (L1),

a first circuit (-8) connecting said first ballast (L1) and said lamp terminals (ll-14) in series between 6. said power terminals (A, C), said first circuit including first switching means (S1, 1, 2) for opening said first circuit; characterized by:

a second inductive ballast (L2) having an ohmic value different from that of the first ballast and magnetically independent thereof,

a second circuit comprising means (9, 10) connecting said second ballast (L2) in parallel with two lamp terminals (12, 14) including one lamp terminal of each pair, and said second circuit comprising connections (7, 8) including switching means (S2, 3, 4) connected between the other lamp terminal (11, 13) of each pair for opening said second circuit,

and means (S) for conjointly opening said first and second switching means thereby to insure that at least one of the inductances applies a voltage pulse across the lamp to ignite the lamp.

References Cited UNITED STATES PATENTS 10/1936 Zecher 315 6/1947 Abernathy 315-99 

1. A FLUORESCENT LAMP STARTING CIRCUIT COMPRISING POWER TERMINALS FOR SUPPLYING ALTERNATING CURRENT TO THE LAMP, FIRST AND SECOND PAIRS OF LAMP TERMINALS, FIRST AND SECOND MAGNETICALLY INDEPENDENT INDUCTANCES, A FIRST CIRCUIT CONNECTING THE FIRST INDUCTANCE ONLY AND EACH PAIR OF LAMP TERMINALS IN SERIES BETWEEN SAID POWER TERMINALS, A SECOND CIRCUIT CONNECTING THE SECOND INDUCTANCE IN PARALLEL WITH TWO LAMP TERMINALS INCLUDING ONE LAMP TERMINAL OF EACH PAIR, AND SWITCH MEANS IN EACH OF SAID CIRCUITS MECHANICALLY COUPLED AND CONJOINTLY OPERATIVE TO OPEN SAID CIRCUITS SO THAT AT LEAST ONE INDUCTANCE APPLIES A VOLTAGE PULSE ACROSS THE LAMP TO IGNITE THE LAMP. 